This makes sense, but for my application it's more important to know the ac voltage with a very light load. The transformer is intended to power a vacuum-relay QSK circuit for an amplifier. It charges a capacitor to the peak voltage, which is applied through a resistor to limit the current through the relays. This reduces the pull-in time of the relays. So what's important to me is the voltage that the capacitor charges to, not the steady state voltage under load!
In this case I just changed the circuit from a bridge to a full-wave ct, bringing the DC voltage down from 200v to 100v, and reduced the value of the series resistor to maintain the proper current through the relays. This should still provide enough 'kick'. I probably could have reversed the transformer and that would have worked as well. On 8/2/2010 9:14 AM, Tom W8JI wrote: > Hi Vic, > > The standard practice is to give secondary voltage with a resistive load > of full rated current. > > Sometimes in special applications the dc voltage output with a specific > rectifier and filter system is given. > > The secondary voltage is dependent on turns ratio, load current, and ESR > of the transformer. We could calculate the secondary voltage if the > manufacturer gave ESR, turns ratio, and if we knew load current. > > If they gave you open circuit voltage, it still would not tell you dc > voltage under load or even peak voltage on the secondary under load. All > it would tell you is zero load current voltage. > > Normal industry standard is to give secondary voltage under full rated > current with a resistive load. This means a 120 volt secondary > transformer is always more than 120 volts RMS without a load or with a > light load. With a capacitor input bridge rectifier would provide > noticeably less than 1.414 times 120 volts at rated current because of > power factor. > > 73 Tom -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
